Imaging Update on Developmental Dysplasia of the Hip With the Role of MRI

Transcription

1 Pediatric Imaging Review Starr and Ha Imaging Developmental Dysplasia of the Hip Pediatric Imaging Review Vanessa Starr 1 o Yoon Ha Starr V, Ha Y Keywords: developmental dysplasia of the hip (DDH), MRI of the hips, musculoskeletal MRI, musculoskeletal ultrasound, pediatric imaging DOI: /JR Received December 20, 2013; accepted after revision March 9, ased on a presentation at the RRS 2013 nnual Meeting, Washington, DC. 1 oth authors: Department of Radiology, Santa Clara Valley Medical Center, 751 S ascom ve, San Jose, C ddress correspondence to V. Starr (vanessaleestarr@gmail.com). This article is available for credit. JR 2014; 203: X/14/ merican Roentgen Ray Society Imaging Update on Developmental Dysplasia of the Hip With the Role of MRI OJECTIVE. The purpose of this article is to review developmental dysplasia of the hip (DDH), a well-described entity previously evaluated with a standard multimodality imaging algorithm, typically consisting of ultrasound and radiography depending on patient age. CONCLUSION. MRI is increasingly used because it is a noninvasive imaging modality that offers excellent anatomic detail, enabling the differentiation of ossified and unossified components of the hip. The radiologist should be aware of the increasing role of MRI and recognize the critical MRI findings of DDH. D evelopmental dysplasia of the hip (DDH) is a disease that involves abnormal development of the femoral head and acetabulum. lthough the precise mechanism of disease pathogenesis has yet to be elucidated, a normal acetabulum stimulates the femoral head to develop adequately and, conversely, an appropriately positioned femoral head enables normal acetabular development [1]. The incidence of DDH ranges from 1.5 to 20 per 1000 births. Multiple risk factors have been described and include breech positioning in utero, oligohydramnios, family history, female sex, and first born [2]. Increased joint laxity in the setting of exposure to maternal estrogens in the perinatal period may also play a role in the development of DDH. The left hip is affected more frequently than the right. Different screening strategies have been described, including clinical examination alone, selective ultrasound screening, and universal ultrasound screening. Selective ultrasound is indicated in patients with associated risk factors or abnormal clinical examinations [3]. common method of screening is serial physical examinations using the arlow and Ortolani maneuvers and selective ultrasound if indicated [4]. The arlow maneuver is performed by adducting a flexed hip and exerting posterior pressure to identify a dislocatable hip. The Ortolani maneuver is performed by abducting a flexed hip with anterior force to relocate an already dislocated hip [5]. Some studies have addressed the effectiveness of universal screening com- pared with selective ultrasound screening [6]. Holen et al. [7] conducted a randomized controlled study comparing the two strategies. Of 15,529 infants after 6 11 years of follow-up, there were five cases of late-diagnosed DDH in the selective group and one case in the general group. Therefore, if universal screening is used, a large number of infants require screening to detect one additional case of DDH. Therapy is most effective and tends to be noninvasive when DDH is detected early [8, 9]. Untreated, DDH can progress to abnormal gait; leg length discrepancies; early osteoarthritis; and, rarely, avascular necrosis [10, 11]. Patients younger than 6 months old are typically braced in Pavlik harnesses [12]. Surgical hip reduction and casting are used for patients who fail the Pavlik harness or those with late diagnoses. Iliac and femoral osteotomies are reserved for severe cases of DDH [13]. Imaging lgorithm Multiple modalities are used for the initial diagnosis and further workup of DDH. The recommended imaging modality for the initial workup depends primarily on patient age (Table 1). In infants up to 4 5 months old, ultrasound is the standard imaging modality. Radiography is recommended thereafter, once ossification of the femoral epiphysis begins to obscure visualization of sonographic landmarks. CT is reserved primarily for problem solving, typically in the postoperative period. It is currently used infrequently because of the disadvantage of ionizing radi JR:203, December 2014

2 Imaging Developmental Dysplasia of the Hip ation. MRI is increasingly used for treatment planning and monitoring. It is now widely used in the postoperative period. Ultrasound Ultrasound is the reference standard for evaluating the hip in an infant before 6 months, when capital femoral epiphyseal ossification usually occurs. It is a nonionizing, quick, and portable examination that furthermore offers the advantage of dynamic imaging in addition to standard static views. The merican College of Radiology recommends that a standard ultrasound examination be performed in two orthogonal planes: a coronal view in the standard plane at rest and a transverse view of the flexed hip with and without stress [14]. Three anatomic landmarks ilial line, triradiate cartilage, and labrum are used to measure the α and β angles. standard plane includes a straight iliac line, the femoral head with maximum diameter, the tip of the echogenic acetabular labrum, and the triradiate cartilage. Figure 1 shows the anatomic landmarks in a normal hip. Meticulous scrutiny of the α angle measurement is necessary because false-positive findings can occur if the imaging plane is suboptimal. When reporting the α angle, the largest angle, not the average angle, should be given. Femoral Head Position Relative to the cetabulum normally positioned femoral head is more than 50% covered by the acetabulum. DDH results in a shallow acetabulum and decreased coverage of the femoral head. Graf α ngle The Graf α angle is measured in the coronal plane and is defined as the angle formed between the vertical cortex of the ilium and the acetabular roof. n α angle less than 60 is abnormal and reflects a shallow acetabulum [15]. Figure 2 shows a normal α angle and Figure 2 shows an α angle in an infant with DDH. The modified Graf grading classification is based on the α angle and degree of acetabular roof coverage (Table 2). Graf β ngle The Graf β angle is formed by a line through the vertical ilium and the cartilaginous acetabular labrum (Fig. 2). Graf β angle greater than 55 is abnormal. With superolateral femoral head displacement, the labrum is elevated, thereby increasing the β angle [16, 17]. TLE 1: Multimodality Imaging lgorithm Modality ge or Indication dvantages and Disadvantages Ultrasound Up to 4 5 mo Unossified femoral head, bony, and nonbony landmarks well evaluated Radiography fter 5 6 mo Once femoral head ossifies, bony landmarks evaluated CT MRI Problem solving, mostly postoperative evaluation Treatment planning and monitoring, including postoperative evaluation TLE 2: Modified Graf Classification Scale Dynamic Harcke Method The purpose of dynamic stress imaging is to determine the position and stability of the femoral head during stress manipulation. Coronal and axial images are obtained in neutral position and hip flexion. The stress maneuver is similar to the clinical arlow examination in which the hip is adducted and pressure is exerted on the knee to force the femoral head to dislocate posteriorly [14]. When monitoring is performed in the Pavlik harness, only static images are obtained [18]. Color Doppler imaging has been used to evaluate perfusion to the proximal femoral epiphysis [19, 20], although there is little literature in the setting of DDH. fter placement of the Pavlik harness, serial follow-up hip ultrasound examinations are performed to assess response to treatment. The infant is left in the Pavlik harness and only static images are obtained [21]. Used for problem solving in past; however, has disadvantage of unnecessary ionizing radiation Treatment planning and monitoring, including postoperative evaluation Graf Type Description α and β ngle Type 1 Normal, mature hip with more than 50% α angle 60, β angle < 55 acetabular roof coverage Type 2a Physiologic immaturity at younger than 3 mo α angle Type 2b Immature at age 3 mo or older α angle Type 2c Extremely deficient bony acetabulum; femoral head is concentric but not stable α angle 43 49, β angle < 77 Type 2d Type 3 Type 4 Femoral head is grossly subluxed and labrum is everted, increasing β angle Dislocated femoral head with shallow acetabulum Dislocated femoral head with severely shallow, dysplastic acetabulum and inverted labrum α angle difficult to measure but is approximately ; β angle > 77 α angle < 43 Radiography fter the child is 4 5 months old, the ossification of the femoral epiphysis begins to obscure sonographic landmarks and radiography becomes more reliable for detection of DDH. This is the standard tool to diagnose DDH after 6 months [22]. n anteroposterior radiograph of the hips in neutral position is used to assess the morphology of the acetabulum, ossification of the femoral head, and position of the femoral head relative to the acetabulum. In early infancy, a normal acetabulum is relatively steeper and straighter. The morphology of the acetabulum changes with age, with the acetabulum becoming more curved inferiorly along the medial and lateral margins. Figure 3 shows the spectrum of normal hips in anteroposterior radiographs in a 6-month-old child and a 2-year-old child, respectively. In DDH, there is delayed ossification of the femoral head and an abnormally shallow acetabulum, thereby predisposing to subluxation and dislocation. dditionally, late complications, such as osteoarthritis and avascular necrosis, can occur. frog-leg lateral view is sometimes used to determine whether a subluxed hip reduces. Several lines and angles are used to diagnose and further characterize DDH (Fig. 3 and Table 3): The first is the Hilgenreiner line, which is a line crossing through both triradiate cartilages. The second is the acetabular angle, which is formed by the Hilgenreiner line and a line drawn through the acetabular roof. neonate should normally have an ac- JR:203, December

3 Starr and Ha TLE 3: Summary of Radiographic Lines and Measurements Hilgenreiner line cetabular angle Perkins line Shenton line Line or ngle Definition Normal Measurement nterior center edge angle etabular angle of less than 30. The acetabular angle should be less than 22 at and beyond 1 year of age [23]. cetabular morphology and the degree of femoral head ossification changes with age (Fig. 3). The third is the Perkins line, which is a vertical line drawn perpendicular to the Hilgenreiner line and intersecting the lateral rim of the acetabular roof. normally situated femoral head is in the inferior medial quadrant. The fourth is the Shenton line, which is a C-shaped line drawn along the inferior border of the superior pubic ramus and the inferomedial border of the femoral neck. normal Shenton line should form a smooth arc [2] (Fig. 3). The fifth is the anterior center-edge angle, which is an angle subtended by a craniocaudal line through the center of the ossified femoral head and a line from the center of the femoral head to the lateral margin of the acetabular roof (Fig. 3). center edge angle less than 20 is indicative of dysplasia [24]. Serial radiography can be used to track disease progression and response to treatment. Figure 4 shows temporal evolution in an infant with mild DDH. Figure 5 shows severe DDH in a 3 year 9 month old child with a late diagnosis. Figure 5 shows the postoperative radiograph in the same patient. TLE 4: Weight-ased 64-MDCT Protocol Horizontal line through both triradiate cartilages ngle subtended by Hilgenreiner line and line through acetabular roof Vertical line intersecting lateral rim of acetabular roof perpendicular to Hilgenreiner line C-shaped line drawn along inferior border of superior pubic ramus and inferomedial border of femoral neck ngle subtended by vertical line through center of ossified femoral head and line from center to lateral margin of acetabular roof rthrography rthrography is typically performed intraoperatively by the orthopedic surgeon at the time of reduction. Obstacles to successful reduction, such as limbus eversion, can be identified. rthrography during reconstructive osteotomy helps obtain concentric reduction of the hip [25] (Fig. 6). CT CT is generally reserved for problem solving in difficult cases and involves a lowdose technique, often in the setting of preor postoperative evaluation (Fig. 7). The CT technique at our institution is weight based (Table 4). CT is more commonly used postoperatively after the patient has been placed in a cast to define the success of reduction [26]. Postoperatively, concentric reduction of the femoral head can be confirmed (Fig. 7). Preoperative assessment includes evaluation of bony acetabular morphology and the ossified femoral epiphysis as well as the femoral head position relative to the acetabulum. recent study compared the use of CT versus MRI to evaluate hip reduction in patients with DDH and found that both modalities offer excellent sensitivity and specificity [27]. CT had sensitivity of 100% and specificity of 96% for the postoperative nonsubluxed hip, whereas MRI showed sensitivity of 100% and a specificity of 100%. Compared with MRI, CT requires shorter imaging time and less, if any, postoperative anesthesia. It is also a useful modality for patients with surgical hardware. However, the primary disadvantage of CT is the exposure to ionizing radiation. MRI MRI Indications MRI, like CT, is often reserved for more difficult cases; however, the major advantage Normal acetabular angle in a neonate is < 30 and < 22 at and beyond 1 year old Normal femoral head should lay in inferior medial quadrant of acetabulum Normal Shenton line should form a smooth arc Normal center edge angle should be > 25 ; angle < 20 indicates dysplasia of MRI is the ability to delineate soft-tissue structures as well as osseous structures without ionizing radiation. Many MRI studies are ordered in the postoperative period, usually after reduction and spica cast placement. In fact, spica cast placement is one of the most common indications for MRI in the setting of DDH. fter open reduction, the hip is held in 90 flexion and partial abduction, and the femoral head is held in position by a plaster spica cast. The degree of abduction must be carefully controlled because too little results in redislocation and too much can increase the risk of avascular necrosis. Neither hip should be abducted more than [28]. Surgeons have varying thresholds and criteria for ordering MRI after spica casting; however, inability to clinically confirm femoral head reduction or abnormal radiography after casting are common indications [29]. MRI Technique One drawback of MRI is the relatively lengthy time of the examination compared with CT or radiography. Protocols differ from one institution to another and the length of MRI examinations has ranged in the literature from as little as 3 minutes to 45 minutes [30 32]. Conroy et al. [29] reviewed the efficiency and accuracy of MRI in confirming femoral head location after closed reduction and spica cast application and concluded that, in their experience, axial STIR MRI was sufficient for confirmation of concentric femoral head reduction. ll of the scans in their study were obtained in less than 5 minutes and none Weight Division (kg) Kilovoltage (kv) Current (m) Slice Thickness (mm) Slice Spacing (ms) Gantry Rotation Speed (s) Pitch < JR:203, December 2014

4 Imaging Developmental Dysplasia of the Hip TLE 5: MRI Protocol Parameters Protocol TR Range (ms) required sedation. Laor et al. [30] also evaluated the utility of limited MRI after surgical reduction for DDH and reported a mean imaging time of 3 minutes for two sequences. Gould et al. [33] found that T2-weighted fast spin-echo sequences were superior with regard to diagnostic performance and were performed in less than 3 minutes. They advised orthopedic surgeons to request axial and coronal T2 fast spin-echo sequences to obtain a diagnostic study in less than 15 minutes, eliminating the need for sedation. t our institution, axial and coronal fast spinecho sequences using conventional fast spinecho or fat-suppressed equivalent T1-weighted and T2-weighted sequences (IDEL, GE Healthcare) are routinely obtained. Ultrafast spin-echo sequences (single-shot fast spin-echo) are sometimes used to decrease scanning time. MRI after spica casting is typically performed in the immediate postoperative period while patients are still under sedation. Gadolinium is not routinely administered. However, if there is concern for avascular necrosis of the femoral head, gadolinium is used to evaluate for femoral head enhancement abnormalities [34]. Table 5 provides the MRI protocol specifications. MRI Findings of the Normal Hip Familiarity with the normal appearance of the pediatric hip on MRI is critical to detect pathology (Fig. 8). The ossified and unossified femoral heads, cartilage, and ligaments are clearly depicted. The infantile acetabulum can be categorized into three basic components: bony, cartilaginous, and ligamentous or soft tissue [35]. The bony acetabulum is seen on radiography and is composed of the acetabular parts of the ilium, ischium, and pubis, all of which are held together by the triradiate cartilage. The cartilaginous acetabulum consists of the hyaline cartilage at the articular surface, which is U- TE Range (ms) Echo-Train Length Flip ngle ( ) No. of Signals cquired shaped and is bridged by the transverse acetabular ligament, and the supporting vascularized growth cartilage, which includes the triradiate cartilage [36]. The labrum, transverse acetabular ligament, and the ligamentum teres are the primary ligamentous structures. The labrum is of low to intermediate signal intensity and appears as a small triangular structure along the edge of the acetabulum on axial images. The labrum s intrinsic signal intensity typically increases slightly from T1- to T2-weighted images [32]. It is important to evaluate for normal morphology and position of the labrum when evaluating dysplastic hips. The transverse acetabular ligament is located inferiorly, where there is a deficiency of cartilaginous acetabulum. The ligamentum teres originates from the transverse ligament and inserts on the femoral head fovea. The iliopsoas tendon is a low-signal-intensity structure that is seen just anteromedial to the anterior labrum on the axial plane. The intraarticular fat pad, or pulvinar, lies in the central portion of the acetabulum and has the highest signal intensity of all the structures in the hip, paralleling that of subcutaneous fat [36]. It is important to assess for pulvinar hypertrophic changes, which can serve as an obstacle to successful reduction. The pulvinar in the affected hip can be compared with the contralateral side to determine any relative size asymmetry. The ossified femoral epiphysis appears as a low-signal-intensity structure within the high-signal-intensity unossified hyaline cartilage. Symmetry between the two ossified femoral heads should be noted. When evaluating for concentric femoral head positioning, a line can be drawn through both triradiate cartilages. fter successful reduction, the ossified portion of the femoral epiphyses should lie anterior to this line [28]. The ossified portions of the anterior and posterior columns are low to intermediate in signal Matrix Slice Thickness (mm) Slice Spacing (ms) Conventional FSE T1-weighted Conventional FSE T2-weighted Fat-suppressed equivalent T1-weighted (IDEL) Fat-suppressed equivalent T2-weighted (IDEL) Note ll studies performed on a 3-T scanner using either a multichannel torso array coil or multichannel neurovascular array coil in axial and coronal planes for each sequence. FSE = fast spin-echo. IDEL manufactured by GE Healthcare. FOV (cm) intensity, with an interposed band of highsignal-intensity triradiate cartilage. Depending on the degree of acetabular dysplasia, the unossified parts of the anterior and posterior columns affect acetabular depth. The fibrous joint capsule attaches to the acetabular margin peripheral to the labrum. t birth, the femoral attachment is near the metaphysis and migrates inferiorly as the hip develops. y 12 months of age, the capsule is partly fused to the femoral neck periosteum and runs up the femoral neck, attaching to the edge of the cartilaginous femoral head [36]. Normal acetabular development is dependent on concentric positioning of the femoral head within the acetabulum. MRI Findings of Developmental Dysplasia of the Hip When characterizing DDH using MRI, the dysplastic acetabulum should be evaluated for retroversion and degree of femoral head coverage. There may be associated cartilaginous defects or delamination. Delayed ossification of the femoral head can be determined by comparing the ossific nucleus of the femoral head in the affected hip with the contralateral side. major advantage of MRI is the ability to visualize the cartilaginous acetabulum and determine its contribution to femoral head coverage. MRI depicts the unossified acetabular epiphysis in the ilium and underlying labrum, therefore showing greater and more accurate acetabular coverage than that seen on radiography alone [37]. Recent orthopedic articles [37 40] have described the utility of bony and cartilaginous acetabular indexes on MRI in the evaluation of DDH. The bony acetabular index can be measured by MRI using an anteroposterior coronal view and is similar to the acetabular index measured on radiography. To obtain the bony acetabular index, the Hilgenreiner line and Perkins line are drawn using the same JR:203, December

5 Starr and Ha TLE 6: Checklist of natomic Structures to Evaluate in Developmental Dysplasia of Hip (DDH) natomic Structures cetabular morphology Symmetry of femoral heads Femoral head position relative to acetabulum Labrum Pulvinar Ligamentum teres or transverse ligament Femoral head perfusion landmarks as used on radiography. The bony acetabular index line is drawn from the Hilgenreiner line at the lateral part of the triradiate cartilage to the Perkins line at the lateral aspect of the bony acetabulum. The angle subtended by the bony acetabular index line and the Hilgenreiner line is the bony acetabular index angle (Fig. 9I). The cartilaginous acetabular index is measured by drawing a line from the lateral part of the triradiate cartilage at the Hilgenreiner line to the lateral acetabular cartilaginous margin (the cartilaginous acetabular index line). The cartilaginous acetabular index angle is formed by the cartilaginous acetabular index line and the Hilgenreiner line [38] (Fig. 9J). Pirpiris et al. [38] compared MRI and radiography in 14 hips with a diagnosis of DDH and no prior surgery to determine the correlation between the bony acetabular index on MRI and the acetabular index on radiography. There was a significant correlation between the bony acetabular index measured on MRI and the radiographic acetabular index. The bony acetabular index and cartilaginous acetabular index also correlated with each other; however, the cartilaginous acetabular index measured significantly less than the bony acetabular index (6.8 ± 3.3 ). Therefore, if bony angle is desired, those authors argue that radiography provides sufficient information; however, MRI provides significant additional information about the true cartilaginous coverage of the femoral head. Li et al. [40] evaluated the bony acetabular index and cartilaginous acetabular index in 81 children with DDH and compared them with 241 healthy control children. In contrast to the study by Pirpiris et al., which showed a significant correlation between the bony acetabular index and cartilaginous acetabular index, Li et al. found that the normal cartilaginous acetabular index decreased rapidly within the first 2 years of life and then remained constant at a mean (SD) of 8.25 (1.65 ) until adolescence. notable difference MRI Findings in DDH Shallow, dysmorphic acetabulum; need to evaluate for retroversion and inadequate femoral head coverage Delayed ossification of femoral head Femoral head subluxation or dislocation Labral hypertrophy; may see mucoid degeneration or tear Pulvinar hypertrophy appears as fibrofatty proliferation Hypertrophy vascular necrosis in the level of dislocation was present between the Tonnis grade in the bony acetabular index and cartilaginous acetabular index. Therefore, bony acetabular development does not always represent cartilaginous development. MRI enables direct and accurate evaluation of the cartilage and important characterization of the cartilaginous acetabular angle [40]. fter successful reduction, the femoral head should be concentrically located in the acetabulum. The angle of abduction can be measured between the main axis of the femur and the midsagittal plane of the subject [31]. This is important to note because too much abduction can lead to avascular necrosis. If contrast material has been administered, the enhancement of the femoral head should be noted. Jaramillo et al. [31] evaluated 23 dysplastic hips immediately after spica casting with contrast-enhanced MRI. They classified the degree of femoral epiphyseal enhancement with a 5-point grading scale, with 1 indicating normal enhancement and 5 indicating globally decreased or absent enhancement. They found a significant correlation between greater abduction and more severe femoral head enhancement abnormalities. In their series, only two of the 14 femoral heads abducted less than 55 showed enhancement abnormalities, and of the hips abducted less than 50, none had enhancement defects. Ray et al. [39] treated late-presented DDH with nonoperative graduated traction and gentle manipulation. They evaluated 12 hips treated as such to confirm concentric reduction. In all 12 hips, there was excellent soft-tissue remodeling around the hip and confirmation of concentric reduction as evidenced by the cartilaginous acetabular extension. Radiography would not have shown the extensive soft-tissue remodeling, and therefore MRI was particularly useful to confirm successful reduction. MRI is particularly useful for determining ligamentous and soft-tissue abnormalities that may serve as obstacles to successful reduction [41]. The fibrofatty pulvinar in the acetabular fossa can become hypertrophied, preventing adequate femoral head reduction (Figs. 10 and 10C). The labrum should be evaluated closely for hypertrophy and abnormal position, such as eversion and inversion (Fig. 10). Similarly, the transverse ligament or ligamentum teres can be hypertrophied and should be routinely evaluated [41]. Rarely, the iliopsoas tendon may be interposed between the femoral head and acetabulum. Table 6 contains a checklist of standard structures to evaluate for DDH. MRI Examples in Two Patients Patient is shown as an example of MRI after spica casting (Figs C). Patient underwent MRI for spica casting first and another MRI later to guide further clinical management (Figs. 9 9J). On occasion, MRI may show discrepant findings compared with radiography. In patient, there was persistent subluxation of the affected hip on follow-up radiography, prompting a second MRI using fat-suppressed equivalent T1- and T2-weighted sequences in anticipation of a possible reoperation. Compared with follow-up radiography, the degree of dysplasia and hip subluxation was not as severe on MRI because the cartilaginous portions of the hip were clearly shown. This case clearly illustrates the utility of MRI because the cartilaginous acetabular index measured 17 whereas the bony acetabular index measured 39, which was concordant with the 34 acetabular angle measured radiographically. The MRI findings led the surgeon to elect less-aggressive management. esides MRI after spica casting, another indication for MRI in the setting of DDH is preoperative identification of potential obstacles to successful femoral head reduction, such as labral inversion, pulvinar fibrofatty proliferation, and transverse ligament and ligamentum teres hypertrophy [41] JR:203, December 2014

6 Imaging Developmental Dysplasia of the Hip Conclusion DDH is a disease that is commonly encountered by both the pediatric radiologist and the general diagnostic radiologist. It has long been evaluated with a standard imaging algorithm, typically consisting of ultrasound and radiography. MRI is increasingly used for problem solving, and familiarity with the MRI findings of DDH is important. References 1. Ponseti IV. Growth and development of the acetabulum in the normal child: anatomical, histological and roentgenographic studies. J one Joint Surg m 1978; 60: Dipietro M, Harcke HT. Developmental dysplasia of the hip. In: Slovis TL, ed. Caffey s pediatric diagnostic imaging, 11th ed. Philadelphia, P: Mosby, 2008: Ortiz-Neira CL, Paolucci EO, Connon T. metaanalysis of common risk factors associated with the diagnosis of developmental dysplasia of the hip in newborns. Eur J Radiol 2012; 81:e344 e Giannakopoulou C, lagizakis, Korakaki E, et al. Neonatal screening for developmental dysplasia of the hip on the maternity wards in Crete, Greece: correlation to risk factors. Clin Exp Obstet Gynecol 2002; 29: U.S. Preventive Services Task Force. Screening for developmental dysplasia of the hip. Pediatrics 2006; 117: Dorn U, Neumann D. Ultrasound for screening developmental dysplasia of the hip: a European perspective. Curr Opin Pediatr 2005; 17: Holen KJ, Tegnander, redland T, et al. Universal or selective screening of the neonatal hip using ultrasound? prospective, randomized trial of 15,529 newborn infants. J one Joint Surg r 2002; 84: Eidelman M, Katzman, Freiman S, Peled E, ialik V. Treatment of true developmental dysplasia of the hip using Pavlik s method. J Pediatr Orthop 2003; 12: Committee on Quality Improvement, Subcommittee on Developmental Dysplasia of the Hip, merican cademy of Pediatrics. Clinical practice guideline: early detection of developmental dysplasia of the hip. Pediatrics 2000; 105: Shipman S, Helfand M, Moyer V, Yawn. Screening for developmental dysplasia of the hip: a systematic literature review for the US preventive services task force. Pediatrics 2006; 117:e557 e Dezateux C, Rosendahl K. Developmental dysplasia of the hip. Lancet 2007; 369: Takahashi I. Functional treatment of congenital dislocation of the hip using Pavlik harness. Nihon Seikeigeka Gakkai Zasshi 1985; 59: Wenger DR, Frick SL. Early surgical correction of residual hip dysplasia: the San Diego Children s Hospital approach. cta Orthop elg 1999; 65: merican Institute of Ultrasound in Medicine. IUM Practice Guideline for the performance of an ultrasound examination for detection and assessment of developmental dysplasia of the hip. J Ultrasound Med 2013; 32: Karmazyn K, Gunderman R, Coley D, et al.; Expert Panel on Pediatric Imaging. CR appropriateness criteria: developmental dysplasia of the hip child D1490.pdf. Published Last reviewed ccessed July 17, Graf R. Classification of hip joint dysplasia by means of sonography. rch Orthop Trauma Surg 1984; 102: Roposch, Graf R, Wright JG. Determining the reliability of the Graf classification for hip dysplasia. Clin Orthop Relat Res 2006; 447: El Ferzli J, buramara S, Eurin D, Le Dosseur P, Dacher JN. nterior axial ultrasound in monitoring infants with Pavlik harness. Eur Radiol 2004; 14: Strouse PJ, DiPietro M, dler RS. Pediatric hip effusions: evaluation with power Doppler sonography. Radiology 1998; 206: arnewolt CE, Jaramillo D, Taylor G, Dunning PS. Correlation of contrast-enhanced power Doppler sonography and conventional angiography of abduction-induced hip ischemia in piglets. JR 2003; 180: Grissom LE, Harck HT, Kumar SJ, assett GS. MacEwen GD. Ultrasound evaluation of hip position in the Pavlik harness. J Ultrasound Med 1988; 7: Starr V, Ha. Developmental dysplasia of the hip (DDH). In: Daldrup-Link HE, Newman, eds. Pearls and pitfalls in pediatric imaging, variants and other difficult diagnoses. New York, NY: Cambridge University Press, 2013: Donnelly LF. Developmental dysplasia of the hip. In: Donnelly LF. Pediatric imaging: the fundamentals. Philadelphia, P: Elsevier, 2009: eltran LS, Rosenberg ZS, Mayo JD, et al. Imaging evaluation of developmental hip dysplasia in the young adult. JR 2013; 200: Grissom L, Harcke HT, Thacker M. Imaging in the surgical management of developmental dislocation of the hip. Clin Orthop Relat Res 2008; 466: Fayad LM, Johnson P, Fishman EK. Multidetector CT of musculoskeletal disease in the pediatric patient: principles, techniques, and clinical applications. RadioGraphics 2005; 25: Chin MS, etz W, Halanski M. Comparison of hip reduction using magnetic resonance imaging or computed tomography in hip dysplasia. J Pediatr Orthop 2011; 31: McNally EG, Tasker, enson MK. MRI after operative reduction for developmental dysplasia of the hip. J one Joint Surg r 1997; 79: Conroy E, Sproule J, Timlin M, McManus F. xial STIR MRI: a faster method for confirming femoral head reduction in DDH. J Child Orthop 2009; 3: Laor T, Roy DR, Mehlman CT. Limited magnetic resonance imaging examination after surgical reduction of developmental dysplasia of the hip. J Pediatr Orthop 2000; 20: Jaramillo D, Villegas-Medina O, Laor T, Shapiro F, Millis M. Gadolinium-enhanced MR imaging of pediatric patients after reduction of dysplastic hips: assessment of femoral head position, factors impeding reduction, and femoral head ischemia. JR 1998; 170: os CF, loem JL, Obermann WR, Rozing PM. Magnetic resonance imaging in congenital dislocation of the hip. J one Joint Surg r 1988; 70: Gould SW, Grissom LE, Niedzielski, Kecskemethy HH, owen JR, Harcke HT. Protocol for MRI of the hips after spica cast placement. J Pediatr Orthop 2012; 32: Tiderius C, Jaramillo D, Connolly S, et al. Postclosed reduction perfusion magnetic resonance imaging as a predictor of avascular necrosis in developmental hip dysplasia: a preliminary report. J Pediatr Orthop 2009; 29: Dwek JR. The hip: MR imaging of uniquely pediatric disorders. Magn Reson Imaging Clin N m 2009; 17: Johnson ND, Wood P, Noh KS, Jackman KV, Westesson PL, Katzberg RW. MR imaging anatomy of the infant hip. JR 1989; 153: Kim HT, Kim JI, Yoo CL. Diagnosing childhood acetabular dysplasia using the lateral margin of the sourcil. J Pediatr Orthop 2000; 20: Pirpiris M, Payman KR, Otsuka NY. The assessment of acetabular index: is there still a place for plain radiography? J Pediatr Orthop 2006; 26: Ray PS, Redden JF, Ward D. Closed reduction of late-presented DDH: MRI view of remodelling. J one Joint Surg r 2003; 85-(suppl II): Li LY, Zhang LJ, Li QW, et al. Development of the osseous and cartilaginous acetabular index in normal children and those with developmental dysplasia of the hip: a cross sectional study using MRI. J one Joint Surg r 2012; 94: tweh L, Kan JH. Multimodality imaging of developmental dysplasia of the hip. Pediatr Radiol 2012; 43(suppl 1):S166 S171 (Figures start on next page) JR:203, December

7 Starr and Ha Fig. 1 Ultrasound of normal hip in 3-month-old boy. and, Standard static coronal () and transverse () ultrasound images of normal hip. Glut = gluteal muscles, c = acetabular cartilage, LTP = ligamentum teres/ pulvinar complex, FH = cartilaginous femoral head, Tr = triradiate cartilage. Fig. 2 Measurement of α and β angles., Ultrasound image shows measurement of α angle (thin diagonal line) in normal hip in 1-month-old boy, which is more than 60 ; β angle (thick line) is also within normal range., Ultrasound image in 1-month-old girl with developmental dysplasia of hip shows α angle (dashed line) is abnormal, measuring 43. cetabulum is shallow and femoral head is laterally dislocated. There is pulvinar fat hypertrophy (arrowhead) and blunting of bony acetabulum (thick solid arrow) JR:203, December 2014

8 Imaging Developmental Dysplasia of the Hip Fig. 3 nteroposterior radiography of hip., Normal anteroposterior radiograph of hips in 6-month-old boy shows acetabular angles in right and left hip (lines) are normal for age, measuring 22 and 24, respectively., Normal anteroposterior radiograph of hips in 2-year-old boy shows α angles of right and left hips are normal for age, measuring 18 and 20, respectively. Note how contour of acetabula changes with age. Ossified femoral epiphyses are symmetric and well seated within acetabula. Hilgenreiner (long-dashed line), Perkins (shortdashed line), and Shenton (dotted line) lines are superimposed. Femoral epiphysis is appropriately situated in inferomedial quadrant. Center edge angle is formed by vertical line through center of femoral head and line from center to lateral acetabular roof (solid lines). Fig. 4 Temporal evolution in girl with mild left developmental dysplasia of hip (DDH)., nteroposterior radiograph obtained at 6 months of age shows shallow left acetabulum with steep roof, compatible with DDH., nteroposterior radiograph obtained at 1 year of age shows interval growth of left femoral epiphysis; however, it remains smaller relative to right femoral epiphysis. Left acetabular dysplasia persists. Fig. 5 3-year 9-month old girl with late diagnosis of developmental dysplasia of hip., Initial radiograph shows superolateral subluxation of right femoral head, valgus deformity, and acetabular dysplasia., Postoperative radiograph after iliac osteotomy and femoral varus osteotomy shows interval healing and improved acetabular roof coverage of femoral head. Previous valgus deformity has been corrected. JR:203, December

9 Starr and Ha Fig. 6 Fluoroscopic image from arthrography in 15-month-old girl with left developmental dysplasia of hip shows contrast material within joint. Femoral head is seated in dysplastic acetabulum. Fig monthold girl with developmental dysplasia of hip (DDH)., Preoperative radiograph showing left DDH., Postoperative CT image was obtained to evaluate relocation of left hip after iliac and femoral varus osteotomy. Fig. 8 Fat-suppressed equivalent T1-weighted image in normal left hip in 11-month-old girl with left developmental dysplasia of hip with structures routinely identified by MRI: = triradiate cartilage, = labrum, C = iliopsoas tendon, D = unossified femoral head, E = ossified femoral head, F = acetabular cartilage, G = acetabulum. Note dysplastic right hip with subluxed femoral head (arrow) JR:203, December 2014

10 Imaging Developmental Dysplasia of the Hip Fig month-old girl with hip click (patient )., nteroposterior radiograph shows lateral dislocation of right hip. Right acetabulum is steep and shallow. Right femoral head ossification is delayed. and C, MRI was performed immediately after right hip arthrogram, closed reduction, and adductor release. xial T1-weighted images show interval reduction of right hip with mild persistent posterior subluxation. cetabulum is shallow. Compared with normal left side (solid arrow, C), right femoral head ossification is delayed (long solid arrow, ). nterior labrum is mildly inverted (short solid arrow, ). Significant pulvinar hypertrophy (dotted arrow, ) was noted. D, Radiograph obtained 6 months after surgery shows interval improvement with mild persistent subluxation of right hip. However, right acetabulum is still dysplastic with abnormal acetabular angle. Right acetabular angle measures 34 and left acetabular angle is 23. (Fig. 9 continues on next page) C D JR:203, December

11 Starr and Ha E G I F H J Fig. 9 (continued) 11-month-old girl with hip click (patient ). E and F, Follow-up MRI was performed to assess whether second operation was indicated. xial (E) and coronal (F) fat-suppressed equivalent T1- weighted images show hypertrophic acetabular cartilage and good morphology of cartilage portion of right femoral head, overall improved since prior MRI. G and H, Coronal non fat-suppressed (G) and fatsuppressed (H) equivalent T1-weighted images show mild right pulvinar fat hypertrophy (arrow) with improved position of femoral head relative to acetabulum since prior MRI. I and J, Coronal T1-weighted images with fat saturation show superimposed bony acetabular index angle (I) and cartilaginous acetabular index angle (J). ony acetabular index measures 39.6, which is fairly concordant with 34 acetabular angle measured on radiographs. Hypertrophic acetabular cartilage contributes to 15 cartilaginous acetabular index, which is still abnormal but relatively closer to normal range (mean cartilaginous acetabular index in 2-year-old is 8.2 ± 1.9 [40]) compared with measured bony acetabular index. This examination served as guide for further orthopedic management. Compared with radiographs, femoral head appears more concentrically located in acetabulum. Surgeon subsequently elected to treat more conservatively JR:203, December 2014

12 Imaging Developmental Dysplasia of the Hip FOR YOUR INFORMTION C Fig month-old girl with hip click (patient )., nteroposterior radiograph shows shallow steep dysplastic left acetabulum (long arrow), lateral subluxation of left hip, and delayed ossification of left femoral head (short arrow). Radiopaque objects seen at bottom of image are buttons overlying patient., xial T2-weighted image with fat saturation obtained after interval reduction and with spica cast in place shows mild residual subluxation of left femur and fibrofatty pulvinar hypertrophy with small effusion. Note signal intensity loss of fibrofatty pulvinar with fat saturation (long arrow). nterior labrum is inverted (short arrow). Right hip appears normal with normal-sized spherical femoral head compared with small and aspherical left femoral head. C, Coronal T1-weighted image shows lateral subluxation of left femoral head and fibrofatty pulvinar hypertrophy (arrow). Note delayed ossification and aspherical shape of left femoral head. This article is available for CME and Self-ssessment (S-CME) credit that satisfies Part II requirements for maintenance of certification (MOC). To access the examination for this article, follow the prompts associated with the online version of the article. JR:203, December